The present invention relates generally to solid rocket propellants, and more particularly to solid rocket propellants, which have a burn rate that is normally only achievable with a Class 1.1 explosive, but have the safety of a Class 1.3 explosive.
A Class 1 explosive is any substance or article, including a device, which is designed to function by explosion (i.e., an extremely rapid release of gas and heat) or, which by chemical reaction within itself, is able to function in a similar manner even if not designed to function by explosion, unless the substance or article is otherwise classed under provision of 49 CFR 173.50. Class 1 explosives are divided into six divisions as follows: (1) Division 1.1 consists of explosives that have a mass explosion hazard. (2) Division 1.2 consists of explosives that have a projection hazard but not a mass explosion hazard. (3) Division 1.3 consists of explosives that have a fire hazard and either a minor blast hazard or minor projection hazard or both, but not a mass explosion hazard, that is, a mass non-detonable hazard rating. Classes 1.4-1.6 are slower burning explosives and are not suitable for rocket propellants.
A need exists for extending the linear burning-rate of tactical (i.e., Class 1, Division 3, or Class 1.3) composite solid rocket propellants for standard ship-borne missiles. The control of burning rate may be viewed as an aspect of energy management, or how the energy initially stored within the solid-propellant charge is allowed to be released. Simplistically, the thrust, F, delivered by a rocket may be expressed as:F=(dm/dt)×Ue, where dm/dt=ρrS, and Ue=Isp×gc 
where dm/dt is the mass evolved by the burning propellant charge per unit time, Ue is the rocket's exhaust velocity, ρ is the solid propellant density, r is the propellant linear burning-rate, S is the total burning surface area of the solid charge, Isp is the propellant specific impulse (which may be thought of as its energy content per unit mass), and gc is the gravitational constant. As the quantities ρ, r, and Isp are intrinsic properties of any solid-propellant composition, one might conclude that a rationale for this need is to increase the volumetric loading of next-generation solid-rocket combustors (i.e., they will become increasingly volume-limited). Hence, energy management (dm/dt, for example) via extrinsic means (e.g., burning surface, S) will become unavailable. A complication is that for current technology compositions (i.e., AP, Al and inert hydrocarbon binder), the chemical kinetics of combustion limits the surface-regression-rate to about 12 mm/sec (0.5 in/sec) at 1,000 psi. Catalytically-accelerated decomposition has been observed to raise this regression rate to 25 to 50 mm/sec (1 to 2 in/sec) at 1,000 psi in some cases, albeit with an increase in hazards (e.g., friction and/or impact). Most notable are with Fe-based liquid Catocene® or ultra-fine solid NanoCat® Fe2O3). However, rates of 125 to 150 mm/sec are cited for the current need.
Such regression-rates have been demonstrated and exceeded in high-energy solid rocket propellants for interceptors (e.g., Sprint, Hibex). However, to achieve both the requisite energy-densities and regression-rates, such propellants, based upon cast composite-modified double-base technology, present mass-detonable (i.e., Class 1 Division 1, or 1.1), and Safety-Life (i.e., long-term life chemical stability) issues. Their hazards when subjected to unplanned insult (e.g., enemy fire) will also be unacceptable for ship-borne ordnance applications. Hence, it will be necessary to maintain a 1.3 hazard classification.
A need exists for a propellant that achieves a burn rate, historically, only attainable using a mass-detonable propellant (e.g., a Class 1 Division 1, or 1.1 explosive). Further, a need exists for a propellant that still meets the Safety-Life (i.e., long-term life chemical stability) acceptable for ship-borne ordnance applications, which heretofore have only been obtainable with propellants classified as a Class 1 Division 3, or 1.3 explosive.
Further, a method is needed for developing a composition of a non-mass-detonable propellant that is highly energetic (where a mass-detonable propellant is a Class 1 Division 1, or 1.1 explosive) and yet meets the Safety-Life (i.e., long-term life chemical stability) acceptable for ship-borne ordnance applications, which is a Division 1.3 hazard classification.